Poppers zwei Definitionsvarianten von 'falsifizierbar'. Eine logische Notiz zu einer klassischen Stelle aus der 'Logik der Forschung'

In paragraph 21 of his "Logic of Scientific Discovery", Karl Popper characterizes with the help of two seemingly synonymous definitions the falsifiability of a theory as a logical relation between the theory itself and its basic statements. It is shown that his definitions do not agree with each other, and this result is applied to the problem of the falsifiability of contradictions, to the difference between falsifiable and empirical statements and to the demarcation criterion.